The University of San Francisco USF Scholarship: a digital repository @ Gleeson Library | Geschke Center Environmental Science College of Arts and Sciences 2014 Modeling Tidal Marsh Distribution with Sea-Level Rise: Evaluating the Role of Vegetation, Sediment, and Upland Habitat in Marsh Resiliency Lisa M. Schile John Callaway University of San Francisco, [email protected] J T. Morris Diana Stralberg V Thomas Parker See next page for additional authors Follow this and additional works at: http://repository.usfca.edu/envs Part of the Environmental Indicators and Impact Assessment Commons Recommended Citation Schile LM, Callaway JC, Morris JT, Stralberg D, Parker VT, Kelly M (2014) Modeling Tidal Marsh Distribution with Sea-Level Rise: Evaluating the Role of Vegetation, Sediment, and Upland Habitat in Marsh Resiliency. PLoS ONE 9(2): e88760. doi:10.1371/ journal.pone.0088760 This Article is brought to you for free and open access by the College of Arts and Sciences at USF Scholarship: a digital repository @ Gleeson Library | Geschke Center. It has been accepted for inclusion in Environmental Science by an authorized administrator of USF Scholarship: a digital repository @ Gleeson Library | Geschke Center. For more information, please contact [email protected]. Authors Lisa M. Schile, John Callaway, J T. Morris, Diana Stralberg, V Thomas Parker, and Maggi Kelly This article is available at USF Scholarship: a digital repository @ Gleeson Library | Geschke Center: http://repository.usfca.edu/ envs/14 Modeling Tidal Marsh Distribution with Sea-Level Rise: Evaluating the Role of Vegetation, Sediment, and Upland Habitat in Marsh Resiliency Lisa M. Schile1,2*, John C. Callaway3, James T. Morris4, Diana Stralberg5, V. Thomas Parker6, Maggi Kelly2 1 Smithsonian Environmental Research Center, Edgewater, Maryland, United States of America, 2 Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America, 3 Department of Environmental Science, University of San Francisco, San Francisco, California, United States of America, 4 Belle Baruch Institute for Marine and Coastal Sciences, University of South Carolina, Columbia, South Carolina, United States of America, 5 Department of Biological Sciences, University of Alberta, Edmonton, Canada, 6 Department of Biology, San Francisco State University, San Francisco, California, United States of America Abstract Tidal marshes maintain elevation relative to sea level through accumulation of mineral and organic matter, yet this dynamic accumulation feedback mechanism has not been modeled widely in the context of accelerated sea-level rise. Uncertainties exist about tidal marsh resiliency to accelerated sea-level rise, reduced sediment supply, reduced plant productivity under increased inundation, and limited upland habitat for marsh migration. We examined marsh resiliency under these uncertainties using the Marsh Equilibrium Model, a mechanistic, elevation-based soil cohort model, using a rich data set of plant productivity and physical properties from sites across the estuarine salinity gradient. Four tidal marshes were chosen along this gradient: two islands and two with adjacent uplands. Varying century sea-level rise (52, 100, 165, 180 cm) and suspended sediment concentrations (100%, 50%, and 25% of current concentrations), we simulated marsh accretion across vegetated elevations for 100 years, applying the results to high spatial resolution digital elevation models to quantify potential changes in marsh distributions. At low rates of sea-level rise and mid-high sediment concentrations, all marshes maintained vegetated elevations indicative of mid/high marsh habitat. With century sea-level rise at 100 and 165 cm, marshes shifted to low marsh elevations; mid/high marsh elevations were found only in former uplands. At the highest century sea-level rise and lowest sediment concentrations, the island marshes became dominated by mudflat elevations. Under the same sediment concentrations, low salinity brackish marshes containing highly productive vegetation had slower elevation loss compared to more saline sites with lower productivity. A similar trend was documented when comparing against a marsh accretion model that did not model vegetation feedbacks. Elevation predictions using the Marsh Equilibrium Model highlight the importance of including vegetation responses to sea-level rise. These results also emphasize the importance of adjacent uplands for long-term marsh survival and incorporating such areas in conservation planning efforts. Citation: Schile LM, Callaway JC, Morris JT, Stralberg D, Parker VT, et al. (2014) Modeling Tidal Marsh Distribution with Sea-Level Rise: Evaluating the Role of Vegetation, Sediment, and Upland Habitat in Marsh Resiliency. PLoS ONE 9(2): e88760. doi:10.1371/journal.pone.0088760 Editor: Just Cebrian, MESC; University of South Alabama, United States of America Received August 30, 2013; Accepted January 12, 2014; Published February 13, 2014 Copyright: ß 2014 Schile et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This paper was prepared in cooperation with the California Bay-Delta Authority for research funded under California Bay-Delta Authority Agreement No. U-04-SC-005 and under CALFED Science Program Grant #1037. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected] Introduction exist as to whether marshes will be able to maintain vegetated elevations. Furthermore, land-use change on adjacent upland Sea levels are projected to rise by 20 to 180 cm over the next habitat, including construction of levees, have restricted opportu- century [1–5]. With such a wide range of sea-level rise (SLR) nities for migration [22–25], likely reducing marsh resiliency with predictions, tidal marsh resiliency is uncertain, as marshes may projected SLR. lose elevation at high rates yet remain stable at lower rates. We An array of marsh accretion models have been used to predict define resilience as the degree to which an ecosystem can maintain marsh responses to SLR, but there are trade-offs between structure and function while withstanding chronic disturbance, in obtaining local-scale predictions using detailed mechanistic models this case increased inundation [6]. Historically, tidal marshes have that include feedbacks between mineral and organic matter inputs responded to increases in sea level by accreting sediment, which is and modeling landscape-level responses of marshes, including affected by feedbacks between mineral [7–9] and organic matter upland migration, at a coarser scale [26]. Many modeling efforts input [10–13], and upland migration [14–16]. However, with have sought to examine how tidal marsh elevations respond to projected increases in sea level, reductions in suspended sediment changes in inundation, suspended sediment concentrations, and/ concentrations that drive mineral accretion [17–19] and decreased or organic contribution due to predicted SLR (for detailed model plant productivity with increased inundation [20,21], uncertainties reviews see [27,28]), and more recent work has examined the PLOS ONE | www.plosone.org 1 February 2014 | Volume 9 | Issue 2 | e88760 Vegetation Influences Modeled Marsh Resiliency impacts of increased temperature [29] and links to carbon plant productivity on modeled marsh resiliency, 3) marsh sequestration potential [30]. Some modeling efforts have utilized resiliency relative to changes in SLR rates and reduction in a hybrid approach, merging results from mechanistic elevation- suspended sediment concentrations, and 4) the importance of based models with digital elevation models to examine projections adjacent upland habitat on marsh resiliency with SLR over 100 at site and landscape levels [31,32]. However, hybrid approaches years. thus far have only mechanistically modeled the mineral contribu- tion to marsh accretion and have not incorporated processes that Methods affect the organic contribution to accretion, or interactions between mineral and organic matter contributions. Multiple Study Area studies have identified the importance of below-ground biomass We calibrated MEM at four historic tidal marshes in the San contribution to vertical accretion [33], sustainability of marsh soils Francisco Bay Estuary (hereafter called Estuary), California, USA [34–36], and resiliency to increases in SLR [37,38]. Therefore, it is that span a salinity gradient from salt to nearly fresh water valuable to integrate these feedbacks of vegetation with inunda- (Table 1, Fig. 1). All sites are 3–5 thousand years old and have tion, elevation, and sediment supply into a hybrid modeling been resilient over time with greatly varying sediment availability approach [11,12]. [40]. China Camp State Park (hereafter called China Camp) is a Across an estuarine landscape from salt to freshwater marshes, salt marsh. Coon Island is a high salinity brackish marsh. Rush the contribution of mineral inputs and organic matter to accretion Ranch Open Space Preserve (hereafter called Rush Ranch) is a can vary depending on tidal marsh location within the estuary. In low salinity brackish marsh. Browns Island is